Header compression (RObust Header Compression, Rohc) is a mechanism that compresses various protocol headers to save transport resources. When a transmitter transmits successive data packets, the sequence number (Series number, Sn) in the protocol header of each data packet ascends, and therefore only a few fields are different in the Sns of adjacent data packets. When an Rohc compressor of the transmitter compresses the Sn of a data packet, the compressor compresses and encodes the fields that are different from the Sns of adjacent data packets to obtain the Sn compression code of the data packet and sends the Sn compression code of the data packet to a receiver.
An Rohc decompressor of the receiver receives the Sn compression code of the data packet and decompresses the Sn compression code of the data packet to obtain the Sn of the data packet. When many successive data packets are lost, the Sn of a data packet obtained by decompression is different from an original Sn of the data packet, thereby reducing accuracy in decompressing the Sn of the data packet.